Microwave Dielectric Properties of CuO-V2O5-Bi2O3-Doped ZnNb2O6 Ceramics with Low Sintering Temperature

Microwave dielectric properties of low temperature sintering ZnNb2O6 ceramics doped with CuO-V2O5-Bi2O3 additions were investigated systematically. The co-doping of CuO, V2O5 and Bi2O3 can significantly lower the sintering temperature of ZnNb2O6 ceramics from 1150 to 870∘C. The secondary phase containing Cu, V, Bi and Zn was observed at grain boundary junctions, and the amount of secondary phase increased with increasing CuO-V2O5-Bi2O3 content. The dielectric properties at microwave frequencies (7–9 GHz) in this system exhibited a significant dependence on the relative density, content of additives and microstructure of the ceramics. The dielectric constant (e r ) of ZnNb2O6 ceramics increased from 21.95 to 24.18 with increasing CuO-V2O5-Bi2O3 additions from 1.5 to 4.0 wt%. The quality factors (Q× f) of this system decreased with increasing CuO-V2O5-Bi2O3 content and ranged from 36118 to 67100 GHz for sintered ceramics, furthermore, all Q× f values of samples with CuO-V2O5-Bi2O3 additions are lower than that of un-doped ZnNb2O6 ceramics sintered at 1150∘C for 2 h. The temperature coefficient of resonant frequency (τ f ) changed from −33.16 to −25.96 ppm/∘C with increasing CuO-V2O5-Bi2O3 from 1.5 to 4.0 wt%